On 2/6/06, Chen Xiao Fan <xiaofan@sg.pepperl-fuchs.com> wrote:
>
> > From: piclist-bounces@mit.edu
> > [mailto:piclist-bounces@mit.edu] On Behalf Of Bob Axtell
> >
> > In most commercial designs of almost any speed, a ground plane is a
> > necessity.
> >
>
> I am not so sure if this is true also for AC/DC and DC-DC converters
> especailly when line voltage are involved. Most likely it is not
> possible to have a "good ground plane" within the high voltage side.

 All mass production (serious) chinese supply designs have a
suplementary ground foil connected with the PCB. Usually is used for
this a single layer 10 mil FR4 continous ground board. The board is
connected with the earth pole
of the mains  connector and acts like a shield.

Vasile

>
> But I will agree that ground plane is important for even not very
> high speed analog circuits if I can afford to have a good ground
> plane. 4-layer boards in general have much better performance for
> our optic proximity sensors but 4-layer boards are much more
> expensive than normal 2-layer boards.
>
> Regards,
> Xiaofan
>
> --
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist